1. Field of the Invention
The present invention relates to a keyless entry system, and in particular, to a keyless entry system that can transmit operation information corresponding to multiple operations on the operation switch.
2. Description of the Related Art
In recent years, a keyless entry system that can perform a vehicle operation such as the locking and unlocking of the door of the vehicle, without using a mechanical key, using radio communication between a portable device carried by the user and an in-vehicle device mounted in the vehicle has come into wide use. The portable device used in such a keyless entry system needs to be small for convenience, and accordingly, the number of operation switches that can be placed in the portable device is limited. Therefore, for example, a keyless entry system that can select a plurality of vehicle operations according to the number of operations of the operation switch has been demanded. In such a keyless entry system, it has become necessary to reliably transmit operation information corresponding to an operation on the operation switch to the in-vehicle device even if the operation is performed multiple times.
As a technique for such a keyless entry system, a keyless entry system 100 disclosed in Japanese Unexamined Patent Application Publication No. 11-081764, a locking and unlocking device 200 (keyless entry system) disclosed in Japanese Unexamined Utility Model Registration Application Publication No. 2-91864, and the like have been proposed. FIG. 6 is an explanatory view showing the configuration of the keyless entry system 100 disclosed in Japanese Unexamined Patent Application Publication No. 11-081764. FIG. 7 is an explanatory view showing the configuration of the locking and unlocking device 200 disclosed in Japanese Unexamined Utility Model Registration Application Publication No. 2-91864.
As shown in FIG. 6, the keyless entry system 100 includes a transmitter 101 (portable device) and a receiver 102 (in-vehicle device). The transmitter 101 includes an operation switch 112, transmission means 113, and transmission control means 111. The operation switch 112 is a switch used when a user gives an instruction to use a function. The transmission means 113 includes an oscillation circuit 114, a modulation circuit 115, and a transmission antenna 116. The transmission means 113 converts a function code (operation information), which indicates the instruction content corresponding to the operation on the operation switch 112, to a remote control signal (radio signal) of the radio wave and transmits the remote control signal. The transmission control means 111 includes a microprocessor 118 and a RAM 119. The transmission control means 111 controls the transmission means 113. The receiver 102 receives the remote control signal transmitted from the transmitter 101 and operates a device 3, which is a keyless entry target, based on the instruction content of the function code included in the received remote control signal.
In the keyless entry system 100, when the operation switch is operated while the transmission processing is being performed by the transmission means 113, a function code corresponding to the operation under transmission processing is stored in transmission control means 111, and the stored function code is converted into a remote control signal to be transmitted by the transmission means 113 after the end of previous transmitting processing. In this manner, in the keyless entry system 100, even if an operation on the operation switch 112 is performed multiple times in a short period of time, it is possible to perform a process of transmitting the function code corresponding to the operation.
As shown in FIG. 7, the locking and unlocking device 200 includes key code transmission means 201 (portable device), a key code receiver 202 (in-vehicle device), and key code verification means 203. The key code transmission means 201 transmits a signal (radio signal) including predetermined key code information (operation information). The key code transmission means 201 transmits a key code multiple times at predetermined intervals. In addition, the frequency of the carrier that carries the key code thereon is controlled so as to be different each time of transmission.
The key code receiver 202 receives a signal transmitted by the key code transmission means 201. The key code verification means 203 compares the key code included in the signal received by the key code receiver 202 with a key code stored in advance, and outputs a locking and unlocking signal when both the key codes match each other.
Although there is no explanation regarding the operation switch in Japanese Unexamined Utility Model Registration Application Publication No. 2-91864, a key code corresponding to the operation on the operation switch can be transmitted by connecting the operation switch to the key code transmission means 201 of the locking and unlocking device 200.
In the keyless entry system 100 disclosed in Japanese Unexamined Patent Application Publication No. 11-081764, even if an operation on the operation switch 112 is performed multiple times in a short period of time, it is possible to perform a process of transmitting the function code corresponding to the operations. However, when the noise of the same frequency as a remote control signal is generated during transmission of the function code, communication between the transmitter 101 and the receiver 102 is interrupted, and accordingly, the receiver 102 cannot receive the remote control signal reliably. As a result, there has been a problem in that it is not possible to reliably transmit the function code. In addition, for example, when only the remote control signal corresponding to the first operation is transmitted despite having performed the operation on the operation switch 112 twice, there is a possibility that the device 3 will operate unlike the intention of the user.
On the other hand, in the locking and unlocking device 200 disclosed in Japanese Unexamined Utility Model Registration Application Publication No. 2-91864, even if the noise of the same frequency as one of the carriers is generated during transmission of the key code, it is possible to transmit the key code using carriers of other frequencies. In the locking and unlocking device 200, however, since the key code is transmitted multiple times at predetermined intervals, it takes time to transmit the key code. For this reason, when the operation on the operation switch is performed multiple times in a short period of time, there is a possibility that the key code may not be reliably transmitted.